FIG. 1 depicts a block diagram of telecommunications system 100 in the prior art. Telecommunications system 100 comprises off-premises telecommunications terminals 101-1 through 101-X, wherein X is a positive integer; on-premises telecommunications terminals 103-1 through 103-X; private branch exchange telephone system 104; and public telecommunications network 105, interconnected as shown.
System 100 is characterized as having two networking regions. Networking region 111 represents the addressable region served by public telecommunications network 105 and comprises the Public Switched Telephone Network (PSTN) or another public network. Networking region 112 represents the addressable region served by private branch exchange 104. As region 112 serves an organization, it is considered to be a “local enterprise network.”
In serving its local enterprise network, private branch exchange 104 is capable of switching incoming calls from network 105 (e.g., the Public Switched Telephone Network, etc.) via one or more transmission lines to any of on-premises terminals 103-1 through 103-N. Private branch exchange 104 is also capable of handling outgoing calls from any of on-premises terminals 103-1 through 103-N to network 105 via one or more transmission lines that connect private branch exchange 104 to network 105.
Private branch exchange 104 is capable of also “extending” an incoming call to a telephone number in network 105, in addition to switching the incoming call to on-premises terminal 103-n, wherein n is an integer between 1 and N, inclusive. The telephone number that is extended-to in telecommunications network 105 corresponds to an off-premises terminal 101-n that is affiliated with a station extension in a database maintained at private branch exchange 104, as depicted by the table in FIG. 2. Off-premises terminal 101-n is typically a wireless terminal, such as a cellular telephone, and does not have to be at a fixed location in networking region 111 when the call is extended to terminal 101-n. 
Often, an organization will have private branch exchanges (PBXs) at two or more different worksites and in multiple countries, in order to serve different regions throughout which the organization's members (e.g., employees, etc.) travel. For example, an employee that travels between worksites in the different countries will want to use his cellular telephone while in or near a “visited” local enterprise network, in order to access, through the visited network, the features back in his “home” network with which his cell phone is affiliated. In other words, an employee who is based at the organization's New York branch office might call the New York office's PBX to invoke a feature such as setting up call forwarding, canceling call forwarding, retrieving voice mail, and so forth, even if the employee is currently at his company's worksite in Germany. In order to properly deliver such a call, the call might be routed through the PBX of the worksite he is visiting (e.g., in Germany, etc.).
Routing a call to the private branch exchange of the visited local enterprise network might be advantageous for a number of reasons, such as for the purposes of providing security, reducing toll charges, because of unavailability of a particular private branch exchange (perhaps based in part on the time zones in which the PBXs are located), and so forth.